While the vast majority of my lyrics searches in MusicBee find success using the indispensable "Lyrics Reloaded (Updated)" plugin, some more obscure metal/goth/darkfolk stuff can be a problem. The "Metal Archives" site (https://www.metal-archives.com
This search string added to custom web links (named whatever) will do a artist/title search at Metal Archives from the MusicBee track information display:
If the song is found and lyrics exist the website will show a "Lyrics" button to the right of the song search results, which when clicked will open a lyrics display window. Then you can select/copy the lyrics, and paste them directly into your file by opening the MusicBee lyrics display window, right-clicking it, and choosing "Paste Clipboard Lyrics into Music File." Afterwards you can do any editing you need via the usual "Edit Displayed Lyrics" choice within MusicBee.